The goal of our research team is to optimize and evaluate compounds that are inhibitors of the delta and epsilon isoforms of casein kinase 1 (CK1?/?). CK1?/? are monomeric serine/threonine protein kinases that regulate diverse cellular processes including Wnt signaling, the DNA damage response and circadian rhythms. Aberrant regulation of CK1?/? is implicated in various cancers, and in neurodegenerative and sleep disorders. Importantly, our research team, which combines expertise in medicinal and synthetic organic chemistry and the derivation of novel therapeutics (PI Dr. William Roush), with those in cancer genetics and preclinical therapeutic studies (co-PI Dr. John Cleveland) and drug development and anti- cancer kinase therapeutics (co-PI Dr. Derek Duckett) has demonstrated that our new in-house and highly selective and ATP competitive CK1?/? inhibitors have very low nanomolar biochemical and anti-cancer (melanoma, breast cancer and glioblastoma [GBM]) cell potency. Furthermore, ex vivo genetic studies in melanoma and triple-negative breast cancer cells indicate that the anti-tumor activity of our compounds is consistent with inhibition of CK1?/? activity and pilot orthotopic xenograft studies have shown that our CK1?/? inhibitors have potent anti-melanoma and anti-GBM activity in vivo. In addition, NCI-60 screens and hollow fiber assays have shown that our CK1?/? inhibitors have remarkable potency against other human cancers that include colon, lung and renal cancer. Importantly, our lead compounds are not generally toxic, as these CK1?/? inhibitors do not compromise the growth or survival of some tumor types or of normal cells and they are well tolerated in chronic 21 day BID dosing in pre-clinical studies. Thus, we hypothesize that the CK1?/? isoforms are highly attractive targets for the development of cancer therapeutics. In Aim 1 the drug-like properties - including brain penetration - of our lead CK1?/? inhibitors will be optimized using reiterative medicinal chemistry, DMPK, and efficacy screens. We will use a rigorous research operating plan to prioritize CK1?/? inhibitors which will flow into studies outlined in Aims 2 and 3. In Aim , using a battery of genetic approaches, we will rigorously test whether the anti-cancer activity of our lead compounds and optimized analogs is solely due to inhibition of CK1? and/or CK1?, or whether other biologically relevant targets contribute to their potency. Using mouse models we also test the roles of CK1? and/or CK1? in the development of mutant BRaf-driven melanoma. Finally, in Aim 3, top compounds will be tested for their anti-tumor efficacy using xenografts of mouse and human melanoma, human triple negative breast cancer, and of primary human GBM both as single agents and in combination with conventional therapies. We submit that our research team will generate a cast of new, potent and safe anti-cancer agents targeting CK1?/? that will be useful as broad-spectrum therapeutics against a host of resistant malignancies.